In the processing of wastewater from industrial processes and wastewater treatment and the like, it has been a common practice simply to discharge the materials to the water, land and air rather than recover the materials for general recycled use. It has been long appreciated, however, that such methods of dealing with these situations are unsatisfactory for numerous and self-evident reasons. As a result of this appreciation, many industries have expended great effort in conducting research into altering the industrial processes to avoid creating the waste in the first place, or to limit its production. However, this adds costs to the industrial process, making the overall process less profitable.
As examples, in the process of converting municipal solid wastes to ethanol, as in U.S. Pat. No. 5,711,817, or in the hydrolysis of cellulosic material, as in U.S. Pat. No. 5,879,637, many valuable byproducts are lost to wastewater treatment because the products are dissolved in the water medium of a concentration too low to warrant the recovery of said products by existing means. Examples of such byproducts from acid hydrolysis that are present as dissolved volatile organic compounds or salts may include but not be limited to glycerol, exlose, levulinic acid, acetic acid, formic acid, furfural, lignin, lignin salts and urea.
Further, the accumulation of dissolved salts, such as urea and organic inhibitors such as furfural, inhibit the reuse of water in a closed loop by requiring recycled water blowdown or discharge to mitigate the accumulation of these inhibitors.
As an example, trace material from a fermentation procedure may be processed in a batch or continuous manner by evaporation, but requires an excessive amount of energy to evaporate large quantities of water. Hence, this evaporation procedure has failed to the extent that is not considered commercially useful. Moreover, the water extracted remains contaminated with volatile organic debris that was made to evaporate in proportion to the vapor pressure balance with water in part by the boiling procedure at or above atmospheric pressures.
The evaporation of water results in an inability to recover the heat of vaporization of the water. This limits the use of evaporation of water as a means of extracting materials of economic interest. Present methods do not integrate or orchestrate the use of cooling and heating in an integrated procedure to make the process adequately efficient to be useful.
Therefore, a need exists for a method of separating liquids such as water from volatile organic compounds and dissolved salts or the like, which method has the ability to recover and recycle heat energy and useful byproducts from the industrial and wastes processing operations.